P. Pennanen

Hybrid meson decay from the lattice

We discuss the allowed decays of a hybrid meson in the heavy quark limit. We deduce that an important decay will be into a heavy quark nonhybrid state and a light quark meson, in other words, the deexcitation of an excited gluonic string by emission of a light quark-antiquark pair. We discuss the study of hadronic decays from the lattice in the heavy quark limit and apply this approach to explore the transitions from a spin-exotic hybrid to

Two heavy-light mesons on a lattice

{\ensuremath{\chi}}_{b}\ensuremath{\eta}

Interactions of heavy-light mesons

and

A Variational fit to the lattice energy of two heavy light mesons

{\ensuremath{\chi}}_{b}S

Four-quark flux distribution and binding in lattice SU(2)

where S is a scalar meson. We obtain a signal for the transition emitting a scalar meson and we discuss the phenomenological implications.

Study of degenerate four-quark states with SU(2) lattice Monte Carlo techniques.

The potential between two heavy-light mesons as a function of the heavy quark separation is calculated in quenched SU(3) lattice QCD. We study the case of heavy-light mesons with a static heavy quark and light quarks of mass close to the strange quark mass. We explore the case of light quarks with the same and with different flavors, classified according to the light quark isospin. We evaluate the appropriate light quark exchange contributions and explore the spin dependence of the interaction. Comparison is made with meson exchange.

Continuum extrapolation of energies of a four-quark system in lattice gauge theory

The potential between static-light mesons forming a meson-meson or a meson-antimeson system is calculated in quenched and unquenched SU(3) gauge theory. We use the Sheikholeslami-Wohlert action and statistical estimators of light quark propagators with maximal variance reduction. The dependence of the potentials on the light quark spin and isospin and the effect of meson exchange is investigated. Our main motivation is exploration of bound states of two mesons and string breaking. The latter also involves the two-quark potential and the correlation between two-quark and two-meson states.

The charge and matter radial distributions of heavy-light mesons calculated on a lattice

Recent lattice calculations on the interaction energy of two heavy-light mesons (Q^2\bar{q}^2) are interpreted in terms of the potential of the corresponding single heavy-light meson (Q\bar{q}). This model leads to a large overestimate of the binding compared with the lattice data -- unless the basic Q\bar{q} potential is modified to become a four-quark potential.

RADIAL CORRELATIONS BETWEEN TWO QUARKS

The full spatial distribution of the color fields of two and four static quarks is measured in lattice SU~2! field theory at separations up to 1 fm at b52.4. The four-quark case is equivalent to a qq¯qq¯ system in SU~2! and is relevant to meson-meson interactions. By subtracting two-body flux tubes from the four-quark distribution we isolate the flux contribution connected with the four-body binding energy. This contribution is further studied using a model for the binding energies. Lattice sum rules for two and four quarks are used to verify the results. The full spatial distribution of the color fields of two and four static quarks is measured in lattice SU~2! field theory at separations up to 1 fm at b52.4. The four-quark case is equivalent to a qq¯qq¯ system in SU~2! and is relevant to meson-meson interactions. By subtracting two-body flux tubes from the four-quark distribution we isolate the flux contribution connected with the four-body binding energy. This contribution is further studied using a model for the binding energies. Lattice sum rules for two and four quarks are used to verify the results. (S0556-2821(98)02223-1)

Comparing improved actions for SU(2)

The energies of four-quark states are calculated for geometries in which the quarks are situated on the corners of a series of tetrahedra and also for geometries that correspond to gradually distorting these tetrahedra into a plane. The interest in tetrahedra arises because they are composed of {ital three} degenerate partitions of the four quarks into two two-quark color singlets. This is an extension of earlier work showing that geometries with {ital two} degenerate partitions (e.g., squares) experience a large binding energy. It is now found that even larger binding energies do not result, but that for the tetrahedra the ground and first excited states become degenerate in energy. The calculation is carried out using SU(2) for static quarks in the quenched approximation with {Beta}=2.4 on a 16{sup 3}{times}32 lattice. The results are analyzed using the correlation matrix between different Euclidean times and the implications of these results are discussed for a model based on two-quark potentials. {copyright} {ital 1995 The American Physical Society.}